Patient monitoring devices and systems

ABSTRACT

In one embodiment, the invention relates to systems, methods, and apparatus relating to the detection of a neuropathy such as a periopertive neuropathy. In one embodiment, a wristband comprising a plurality of anodes and cathodes is used. The wristband can be a component in a electrode array that includes a plurality of reference or recording electrodes. The electrode array can be configured to stimulate and collect responsive signals from an ulnar, a median, radial and posterior tibial nerve. The simulation and signal collection can be performed on a continuous basis for time periods of interest such as a given perioperative time period using a monitoring device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/643,490 filed May 7, 2012, the entire disclosure of which isincorporated by reference herein.

FIELD OF THE INVENTION

The invention relates generally to the field of patient monitoring andsafety. In part, it specifically relates to the monitoring ofsomatosensory electrical potentials to identify one or more patientstates or neuropathies.

SUMMARY OF THE INVENTION

In part, the invention relates to a nerve monitoring system. In oneembodiment, the invention includes a non-invasive hand-held monitoringsystem that tests the integrity of the central and peripheral nervoussystem. This automated test uses electrodes to generate input signalsand receive responsive output signals. These signals can be processed todetect and prevent intraoperative positioning related neuropathies. Inone embodiment, the invention relates to an electrode array thatincludes a first and a second wrist electrode such that each isconfigured to simultaneously and/or sequentially stimulate three nerves.

Preventing perioperative neuropathy in the peripheral nervous system hasmany challenges. One challenge arises from the multiple, variablycross-linked tracts of the peripheral nervous system. Nerve injury fromperioperative positioning can occur anywhere along the tracts of theperipheral nervous system. Testing the integrity of an ascending tractthat is being stimulated can miss branches of the brachial plexus.Monitoring several nerves can address this issue. In addition, by usinga wristband-based electrode suitable nerves can be monitored withsufficient accuracy and quickly deployed for monitoring without havingthe electrode placer undergoing extensive training relating to electrodeplacement.

In one embodiment, the invention relates to a monitoring systemconfigured for widespread peripheral/dermatomal evoked potentialmonitoring. Monitoring such potential signals increases detection ofupper extremity neural dysfunction. This increase occurs by effectivelystimulating and monitoring traffic through the various and unpredictablebranches of the brachial plexus. Widespread transdermal stimulation andmonitoring can detect more events of interest and thus prevent moreperipheral neural dysfunction.

Using widespread peripheral/dermatomal sensory evoked potentials allowsoperators to monitor and evaluate nerve health and function. Raw evokedpotentials, a type of responsive signal generated from stimulatednerves, can be digitized and processed to convey interpretable data andhuman-readable alerts. These alerts can indicate a neuropathy or otherstate of interest relating to the nervous system such as limb positionand nerve compression.

In part, the invention relates to devices and methods for implementingcontinuous peripheral nerve monitoring. This monitoring can be performedrelative to one or more established baseline values. This comparison ofresponsive signals from stimulated nerves to a baseline allows detectionof various potential neuropathies and changes in patient states such asposition states. For example, significant changes in nerve conductioncan be identified and triggered upon. A given limb position can compressa region and cause nerve damage if unresolved in time. Alerts can thenbe generated to prompt intervention and thus prevent peripheralneuropathies causing patient discomfort or injury. This monitoringmethod can be used as a standard of care for all operations and otherscenarios that cause neuropathies.

In one embodiment, the invention includes a computer-based system andmethods configured for widespread peripheral/dermatomal somatosensoryevoked potentials monitoring. In one embodiment, an electrode array canbe used along with a monitoring system to evaluate the entirebrachioplexus for time periods of interest. As a result, missedoperative positioning neuropathies that could be missed can beprevented. Non-invasive monitoring configured to avoid dermal needleplacement is another embodiment of the invention. In one embodiment, anelectrode array is one aspect of the invention. A suitable electrodearray can include a plurality of stimulating electrodes and a pluralityof recording or reference electrodes.

In one aspect, the invention relates to a nerve monitoring system. Thesystem can include a wristband. The wristband can include a first pairof electrodes, a second pair of electrodes, a third pair of electrodes,and an elongate flexible substrate, first electrode, second electrode,and third electrode disposed in or on the flexible substrate; and afirst electrical lead having an electrode contacting end and amonitoring device contacting end, the electrode contacting end inelectrical communication with at least one electrode in the first pairof electrodes.

In one embodiment, the first pair of electrodes is positioned relativeto the elongate flexible substrate such that each electrode in the firstpair is positionable above a median nerve when the wristband is worn.The second pair of electrodes can be positioned relative to the elongateflexible substrate such that each electrode in the second pair ispositionable above a radial nerve when the wristband is worn. The thirdpair of electrodes can be positioned relative to the elongate flexiblesubstrate such that each electrode in the third pair is positionableabove an ulnar nerve when the wristband is worn.

In one embodiment, the flexible substrate has one or more demarcationsconfigured to identify a boundary between one or more nerves or bonesdisposed relative to nerves. The system can further include a secondelectrical lead having an electrode contacting end and a monitoringdevice contacting end, the electrode contacting end in electricalcommunication with at least one electrode in the second pair ofelectrodes. The system can further include a third electrical leadhaving an electrode contacting end and a monitoring device contactingend, the electrode contacting end in electrical communication with atleast one electrode in the third pair of electrodes. The system canfurther include a monitoring device in electrical communication with themonitoring device contacting end of the first electrical lead, themonitoring device configured to stimulate one or more electrodes in thefirst electrode pair and monitor responsive signals from one or more ofa radial, ulnar or median nerve.

In one embodiment, the monitoring device includes a housing, one or moreelectrode input ports configured to connect to one or more electricalleads, a processor disposed in the housing, a memory storage deviceconfigured to store measured baseline signals, a timer configured tosynchronize pulse delivery, a pulse generator configured to transmit aplurality of pulses along the first electrical lead, a comparatorconfigured to detect deviations in responsive nerve signals generatedfollowing pulse delivery to a nerve, and an alarm generator configuredto indicate a change from a first patient state to a second patientstate, the memory storage device, the timer, the pulse generator, andthe comparator in electrical communication with and responsive toprocessor control signals. The system can further include an adapterconfigured to interface with an anesthesia machine such that alerts,nerve signals, or combinations thereof are presented on a display of theanesthesia machine.

In one aspect, the invention relates to processor-based method ofdetecting a neuropathy in a patient. The method includes noninvasivelymonitoring a first nerve, a second nerve, and a third nerve, wherein thefirst nerve, the second nerve, and the third nerve are at leastpartially disposed in the wrist of the patient; electrically stimulatingthe first, second, and third nerves; detecting a deviation relative to abaseline signal with respect to a responsive signal generated by one ormore of the first, second, and third nerves following the electricstimulation using a processor; comparing the deviation to apredetermined threshold using a processor; and generating an alertindicative of the neuropathy when the deviation exceeds a predeterminedthreshold. In one embodiment, the neuropathy is a perioperativeneuropathy and the alert is displayed on an anesthesia machine. In oneembodiment, the first nerve is a radial nerve, wherein the second nerveis a median nerve and wherein the third nerve is an ulnar nerve. Themethod can further include noninvasively monitoring a fourth nerve atleast partially disposed below a knee of the patient. In one embodiment,the fourth nerve is a posterior tibial nerve and wherein the responsivesignal is generated by one or more of the first, second, third andfourth nerves.

In one aspect, the invention relates to a nerve monitoring system. Thesystem includes an input port configured to receive a plurality of timevarying electrical signals from one or more reference electrodes in anon-invasive electrode array; a comparator in electrical communicationwith the input port; a processor in electrical communication with thecomparator; a display device in electrical communication with theprocessor; and a memory device storing a plurality of instructionswhich, when executed by the processor, cause the processor to operatewith the display device and the comparator to: control the comparatorand cause it to compare one or more of the plurality of time varyingelectrical signals to one or more baseline signals; determine when adeviation between a baseline signal and one or received signals from theelectrode array exceeds an alarm threshold; and control the displaydevice such that an alarm signal is displayed when the alarm thresholdhas been exceeded.

In one embodiment, the non-invasive electrode array is configured tocollect signals from N+M positions on a patient by contacting a skinsurface without piercing the same. The electrode array can include a Nanode and cathode pairs and M reference electrodes such that each anodeand cathode in a pair is positioned to stimulate one or more monitorednerves and each reference electrode is positioned to measure one or morebaseline nerves or baseline positions. In one embodiment, N is greaterthan or equal to six and M is six. In one embodiment, the monitorednerves include a radial nerve of a first hand, an ulnar nerve of thefirst hand, a median nerve of the first hand, a radial nerve of a secondhand, an ulnar nerve of the second hand, and a median nerve of thesecond hand. In one embodiment, the monitored nerves further include aposterior tibial nerve of a first foot and a posterior tibial nerve of asecond foot. In one embodiment, the baseline nerves or baselinepositions include FPz, a first Erbs point, a second Erbs point, and aCV.

In one aspect, the invention relates to an electrode array configured togenerate and monitored evoked potentials. The electrode array includes awristband that includes a first pair of electrodes, a second pair ofelectrodes, a third pair of electrodes, and an elongate first flexiblesubstrate, a second substrate disposed on the first substrate, the firstelectrode, second electrode, and third electrode disposed in or on thesecond substrate, wherein one electrode in each pair is an anode and theother electrode in each pair is a cathode, wherein all three anodes arearranged substantially in a first row and wherein all three cathodes arearrange substantially in a second row. In one embodiment, the secondsubstrate is a gel.

In one embodiment, the monitoring device can include a housing, one ormore electrode input ports configured to connect to one or moreelectrical leads, a processor disposed in the housing, a memory storagedevice configured to store measured baseline signals, a timer configuredto synchronize pulse delivery, a pulse generator configured to transmita plurality of pulses to a the first electrical lead, a comparatorconfigured to detect deviations in responsive nerve signals generatedfollowing pulse delivery to a nerve, and an alarm generator configuredto indicate a change from a first patient state to a second patientstate, a neuropathy or a potential neuropathy.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention can be better understood withreference to the drawings described below, and the claims. The drawingsare not necessarily to scale, emphasis instead generally being placedupon illustrating the principles of the invention. In the drawings, likenumerals are used to indicate like parts throughout the various views.The drawings associated with the disclosure are addressed on anindividual basis within the disclosure as they are introduced.

FIG. 1 is a schematic diagram of various components of a nervemonitoring system according to an illustrative embodiment of theinvention.

FIG. 2 is a schematic diagram of an electrode array that includesstimulation electrodes and baseline or reference electrodes according toan illustrative embodiment of the invention.

FIG. 3 is a schematic diagram of another electrode array shown relativeto a patient according to an illustrative embodiment of the invention.

FIG. 4 is a series of stages or processing steps associated withconfiguring and collecting data associated with monitoring a patientduring an active period according to an illustrative embodiment of theinvention.

FIGS. 5A-5C are diagrams showing different electrode configurationssuitable for applying to a wrist according to an illustrative embodimentof the invention.

FIGS. 6A-6C are schematic diagrams showing two cross-sectional views anda top view of an exemplary wristband-based electrode according to anillustrative embodiment of the invention.

FIG. 7 is a schematic diagram of a monitoring system according to anillustrative embodiment of the invention.

FIG. 8 is a user interface screen showing evoked potential signalsvarying over time and various indicators suitable for evidencing analarm, system status, or normal state according to an illustrativeembodiment of the invention.

FIG. 9 is a series of plots showing time varying evoked potentialsignals associated with one or more nerves according to an illustrativeembodiment of the invention.

FIGS. 10A-10F show individual views of the signal plots shown in FIG. 9according to an illustrative embodiment of the invention.

DETAILED DESCRIPTION

The following description refers to the accompanying drawings thatillustrate certain embodiments of the present invention. Otherembodiments are possible and modifications may be made to theembodiments without departing from the spirit and scope of theinvention. Therefore, the following detailed description is not meant tolimit the present invention, rather the scope of the present inventionis defined by the claims.

In one embodiment, the invention relates to a non-invasive electrodearray that can be used in conjunction with a system or device to monitorperipheral nerve conduction and detect a change in nerve function inresponse to stimulation signals. These changes in nerve function can beidentified based on deviations from predetermined thresholds. Detectingthe change can be used to alert an operator to prevent positioninginduced neuropathies such as neuropathies from operative positioning.The device or system can be a portable and/or a hand held deviceconfigured to connect with the electrode array. Once connected, thedevice or system can selectively stimulate certain nerves via one ormore electrodes and monitor the same. The system or device can also beincorporated in an anesthesia machine or other machine used in a patientdiagnosing or treating environment.

In one embodiment, an exemplary monitoring system includes foursubsystems or processing stages. Such an exemplary system is depicted inFIG. 1. The system 10 can include, without limitation, a patientinterface subsystem or stage 12; an input/output subsystem or stage 14;a data processing subsystem or stage 17; and an alarm detectionsubsystem or stage 18. Various other subsystems or processing stages canbe used and the individual components of a given monitoring system canbe grouped and categorized in different ways. The patient interface canbe in electrical communication with an electrode array. The electrodearray can include a plurality of stimulation electrodes 20 and aplurality of recording or reference electrodes 23.

The stimulation electrodes 20 are positioned to contact the skin of apatient in order to stimulate a plurality of peripheral nerves. In oneembodiment, three peripheral nerves are stimulated. In anotherembodiment, four peripheral nerves are stimulated. These nerves caninclude a Radial nerve 21 a; a Median nerve 21 b; an Ulnar nerve 21 c;and a Posterior Tibial nerve 21 d. In one embodiment, electrodes are geltype electrodes. These electrodes are configured to stick or adhere to apatient in one embodiment. The recording electrodes 22 can be configuredto record relative to FPz 23 a, one or both Erb's points 23 b, and at CV23 c.

The input subsystem 14 a can include an impedance circuit, a pulsegenerator, an isolator, and energy source. The output subsystem 14 b caninclude an analog to digital converter and an amplifier pre-processor.The data processing system 17 can include an averager, a timer, afilter, a processor, memory storage, and a comparator. In addition, thealarm detection subsystem 18 can include an alarm decision module(software or hardware based) and an output such as a display device or aspeaker to announce an alarm. The output system 14 b is in electricalcommunication with the recording electrodes 23 while the input system 14a is in electrical communication with the stimulation electrodes 20.

The monitoring device or system used in a given embodiment can eliminatethe need for human analysis. The device or system is automated bysoftware that works with a processor to detect preset thresholds tosignal a change from the baseline reading. The software can then alertthe anesthesiologist or other operator to reposition an extremity tore-establish the baseline waveform.

System, methods, and devices can use widespread peripheral/dermatomalevoked potential recordings. They can detect upper extremity neuraldysfunction by stimulating and monitoring traffic through the branchesof the brachial plexus. Since this traffic can be the variable anddifficult to predict, the electrode array described herein is configuredto increase the predictability by being selective and considering a setof three or more nerves as part of the stimulation and monitoring. Anexemplary electrode array 24 is shown in FIG. 2 and can include variousstimulating and recording electrodes as described herein. In oneembodiment, the stimulating electrodes can be configured as part of awristband configuration or as a wrist electrode as shown in FIG. 3.

In FIG. 3, various stimulating and record electrodes are disposed on theskin of a patient. These electrodes can be used to monitor for variousevents of interest as detected by changes in responsive signalsfollowing electrode stimulation. The nerve signal changes whenelectrical stimulation is delivered at the wrist nerves and/or at theposterior tibial nerves. The recording electrodes capture and relay suchchanges as outputs for pre-processing and other processing steps by agiven system embodiment such as that shown in FIG. 7. When a nerve iscompressed or otherwise changed by a patient's position, such signalscan be detected.

In one embodiment, use of all three nerves offers various advantages.Due to the anatomical variability and even the normal distribution ofnerves in the brachial plexus it has been discovered that monitoring asingle nerve for positional related nerve damage should include themonitoring of all the major nerves that pass through the wrist. Whilemonitoring a single nerve (most commonly either the Ulnar nerve or theMedian nerve) injuries can be missed. Monitoring only a single nerveresults in a few patients awaking from anesthesia with some injuries.Monitoring all three nerves has resulted in no permanent injuries duringexperimental trials. Thus, in part, the invention relates to thediscovery that monitoring of these three nerves can result in asignificant increase in patient safety by reducing or stoppingpositional injuries.

FIG. 4 describes a process flow 25 for a series of steps that can beperformed to monitor a patient during an operation, experiment, clinicaltrial, or under other circumstances. Initially, the patient is medicatedor receives anesthesia through lines (Step 27). Either before or afterthis step, stimulation electrodes such as a wrist electrode arepositioned relative to the nerves to be stimulated (Step 29). Therecording electrodes or other electrodes can then be positioned (Step31). A system self-test can then be performed (Step 32). Data from therecording electrodes can be processed using a processor to perform anauto-configuration such that baseline nerve data can be acquired (Step34). Continuous monitoring can be performed for an active period such asthe operation time period or another time period (Step 23). If changesto the baseline signals deviate from one or more thresholds asdetermined by a processor or other device component an alarm isgenerated to indicate that a patient should be moved or that furtheroperate involvement may be needed (Step 37).

In one embodiment, a wristband that is connected to one or more of thestimulation electrodes is used. Such a wristband can be used tostimulate a first and second or a first, second, and third nerve bundleas described herein. FIGS. 5A-6C show further details relating to usingelectrodes for nerve monitoring relative to a wrist.

As shown in FIG. 5A-5C, the wristband 40 can include a flexiblesubstrate 45 having an elongate or rectangular configuration. Thesubstrate is sized and configured to cover some or all of the wrist andstably position stimulation electrodes relative to nerves in the wrist.The wristband 40 can be configured for quick placement on the wrist. Inone embodiment, all three upper peripheral nerves are monitored (radial,ulnar and median) to avoid missing branches of the brachial plexus. Inone embodiment, the nerves are monitored in and interleaved sequentialfashion. In another embodiment, the nerves are monitored sequentially.One or more electrical leads 46 can be in electrical contact with agiven electrode or anode/cathode pair. The electrodes can be gelelectrodes in one embodiment. The systems described herein can monitorthe lower extremity perineal nerve for lower extremity positioningneuropathies as shown in FIG. 3. Widespread transdermal stimulation andmonitoring can detect and thus prevent more peripheral neuraldysfunction missed by conventional SSEP monitoring. In one embodiment,widespread transdermal stimulation refers to activating or stimulatingmultiple nerves instead of just a single nerve.

FIGS. 5A and 5B shows the configuration of the electrodes placed on thewrist. Stimulation electrodes are placed in positions superficiallyperipheral nerves of interest. The wrist electrode can include sixelectrodes (anode and cathode for the three wrist nerves). A second setof electrodes that can be used as components of the electrode arrayinclude reference or recording electrodes. An exemplary representationof these recording electrodes is shown in the electrode array of FIG. 3and FIG. 4. In one embodiment, the recording electrodes are also gelelectrodes configured to stick to the patient's skin electrodes. Theyare sized and sufficiently flexible to be positioned at the bilateralErb's points, FPz (frontal pole at midline) and CV. These electrodes,along with the stimulation electrodes, are shown in FIG. 3.

Needleless cortex monitoring is one advantage of the electrode array ofFIG. 3. In one embodiment, the recording electrodes are configured tocontact the skin to record nerve signals without piercing the skin.Thus, these electrodes are needleless in one embodiment. These types ofelectrodes are safer and result in a more user friendly experience. Theyalso increase the likelihood that the system will be used by avoidingneedle placement.

In one embodiment, all the wrist electrodes are contained in a singlegel pack which can constitute a substrate. The substrate can beseparated, stretched and modified as needed to allow for anyconfiguration of the arterial line or wrist anatomy. Electrode positionsin the wrist electrode are designed to improve operator use and preventfailing to monitor all three nerves. In one embodiment, the substrateforming the wristband that has anodes or cathodes disposed thereon canstretch and flex so that electrode position can be adjusted. In anotherembodiment, the anode and/or other the cathode portions of eachelectrode can be removed and repositioned relative to the substrate. Inthe case of some electrodes one or more substrate can be used such as abacking substrate and a gel substrate disposed thereon. The electrodesand substrate are sterile in one embodiment.

The wrist electrode is a multi-component device configured to providelow noise signals generated in response to evoked potentials to amonitoring system. All six electrodes can be applied at one time and canbe used to secure any monitoring line for anesthesia (also referred toas an A-line) in place. Thus, the wrist electrode can be used to secureother electrodes while monitoring the wrist nerves. One issue withstandard electrode placement is the securing tape used with one or moreA-lines gets in the way. In order to address that problem the wristelectrode can be made of a flexible transparent dressing material suchas Tegaderm. The anode and cathode for each electrode pair can bedisposed on such a substrate 45 with the leads 46 flowing outwards to amonitoring device. The electrode kit that includes a wrist electrode caninclude Mastisol® to help secure the electrode or components thereof.

In one embodiment, an operator places three sets of electrodes over eachof the main nerves at the wrist (the Ulnar, Median, and the Radial) forstimulation. This requires knowledge of the anatomy. It is also timeintensive to place the six electrodes (anode and cathode for eachstimulation pair). In order to improve the efficacy and the accuracy ofplacement for the untrained user, a single device where each pair isencased or disposed in a band is used as shown in FIG. 5B. The band ismade of a comfortable material with embedded gel electrodes. Sixelectrodes are used in one embodiment (three anodes and three cathodes).In one embodiment, there are three marks on the band to help in properanatomic placement. The first mark is in the center of the band and willline up with the center of wrist. There are two lateral marks that will,when properly placed lie over the ulna and radius bones.

Material between the center pair of electrodes and the two lateralelectrodes can be adhesive-free. Thus, that area to forms a fold for asmaller wrist. Adhesive is placed at the lateral segments of the band,under the electrodes and in the middle of the band to help hold the bandin place in one embodiment. The segments with no adhesive allow for bandposition modifications due to A-line placements.

In one embodiment, the wristband will have two removable protectivecovers disposed over the adhesive. Removal of the first protective coverwill expose a light abrasive pad with alcohol. This is rubbed over thewrist to improve the contact between the electrodes and the wrist. Inturn, this reduces the contact resistance and improving the deliveredstimulation signal. After cleaning, the wrist this pad is removedexposing the adhesive and electrodes. Due to the variation in A-lineplacement techniques some modification of the A-line securing tapeand/or placement of the stimulation leads may be needed in someembodiments.

FIGS. 6A-6C show various cross-sections of a wrist electrode withanode/cathode pairs for each of Radial nerve R1/R2, Median nerve M1/M2,and Ulnar nerve U1/U2. Each anode is a type of electrode in oneembodiment. Each cathode is a type of electrode in one embodiment. Thesubstrate 45 can be fabricated from a mesh, a tape, multiple substrates,gels, and other materials. Elements A1 and A2 can be disposed in or onesubstrate 45 and provide a demarcation or boundary to guide any enduser. The elements A1, A2 can be tape, pigments, dyes or othermaterials. Other lines or boundaries can be disposed in or on thesubstrate to facilitate proper placement. The only element that needs tocontact the skin is the surface of each electrode. As a result, thewristband need not adhere to the skin at every region along its skincontacting side. Accordingly, in one embodiment the space between eachelectrode can be adjusted by folding for different wrist sizes.

FIG. 7 illustrates an example monitoring system 50 including a processor53 and various other components. An exemplary housing 51 is shown. Theinput/output interface can include a pulse generator 55 and one orpre-amplifiers 56. These can be isolated from other system componentsusing an isolator or other devices 57. The pulse generator 55 caninclude a power source connected to the isolator. In one embodiment, thepulse generator energy source is optically isolated from the mainprocessor and pulse generating circuit. These can be separate elementsin one embodiment of the monitoring system. Each pre-amplifier is inelectrical communication with an electrode or lead or cable connectedthereto. This arrangement minimizes or reduces external noise.

The pulse generator 55 can either be disposed inside the housing of themonitoring device or at the electrode connectors. The pulse generator 55defines properties of the pulses and generates the actual pulse based onthe timing circuit 66. The processor 53 defines the pulses by definingthe amplitude and pulse width of the pulse.

Once the pulse is initiated at the pulse generator, it passes throughthe isolation and energy source circuit 57 for delivery to the patientthrough stimulation electrodes. This circuit isolates the patient fromthe major AC line signal in order to protect the patient from anygrounding or line failures. It also contains protection circuitry toprotect the stimulator from stray spikes from cautery or externaldefibrillators. At specified time intervals, the processor halts thecollecting of data for a specified time. During this halt state itchecks the impedance of each electrode. This is to assure that thesystem is properly working. This circuit can also be initiated if thesystem starts to detect excessive noise or other artifacts. When thesystem detects frequencies in the band of the cautery devices theprocessor will not initiate this circuit. Recording is performed bycircuitry at units close to the electrodes on the patient and digitizedat those areas. This configuration minimizes or reduces noise enteringthe system.

The processor 53 performs various actions and steps in the system 50. Itgenerates the timing for the stimulation signal to each nerve bycontrolling timer 66. The pulses to control both the data acquisitionand the averaging system also referred to as the averager 64 aregenerated by the processor 53. The programming of the alarm criteria canbe performed using instructions that execute on the processor 53. Thecomparison algorithm and the error checking can also be performed by theprocessor.

In one embodiment, the processor contains or is in electricalcommunication with a digital signal processor for signal processing. Thetimer 66, after receiving the appropriate signals from the processor 53,controls the sequence of stimulation (i.e. when each stimulator willfire) a control signal imitates the start of the specific average forthe recording of that electrical or evoked potential.

In one embodiment, each nerve is checked in a sequential fashion. Thetiming circuit or timer 66 controls that sequence and also theappropriate averaging sequence at the instruction of the processor 53.After the initial baseline signals are acquired and stored, theprocessor 53 executes a running average algorithm, or multiple averagedalgorithm (depending upon the user configuration or internaldetermination of the noise level in the system) to compare the inputsignals to the stored baseline. The baseline signal can be stored in amemory storage device 73. This continues over a time period T in oneembodiment. T can correspond to a perioperative time period in oneembodiment.

If the comparator 71 determines a significant discrepancy between thebaseline and the real-time signal, then an alarm decision 68 is made.This can be subject to a determination that the noise level isconsidered acceptable. This can reduce false triggering and alarming.Various filters 65 and other components can be used to reduce signalnoise. Once an alarm state is generated in response to a threshold orother parameter being detected, an alarm signal is sent to an output 70.The output can be a display, an indicator, such as an LED, or a speaker.

In one embodiment, a subsequent step in the process includestransmitting the digital signal to an averager 64 as shown in FIG. 7. Acontinuous moving average is used by the system 50 in some embodiments.Software is used in conjunction with the processor to determine suitableor optimal averaging weights based on room noise and signal quality.This is defined for each signal received from an electrode andcontrolled by the processor 53. Filtering of the signal removes unwantedelements of the signal, such as EKG artifact, if needed based on a noisethreshold. Enhancing low SNR signals using specific signal techniques(i.e. wavelets) to extract the signal in the least amount of averagingcan also be performed.

Prior to continuous averaging, a baseline signal is obtained forcomparison. The baseline signal is recorded at the start of anoperation, but can also be initiated at any time by the end user. A newbaseline can be selected in response to modifications in the anesthesiatechnique or type, electrode changes, modifications in the externalsignal artifices and based on other factors.

Each nerve's baseline is stored independently such as in memory storage73. This baseline signal is used as one input to the comparator 71. Oncethe baseline signal is stored, the output of the moving average iscompared relative to the baseline at various time periods. Thecomparator thresholds and morphology parameters are controlled by theprocessor 53. If a change that has occurred on the waveform passes anyof these thresholds the comparator 71 sends a signal to the processorand to the alarm decision unit. Depending upon the state of the system50, as defined by the processor, the alarm decision unit or module 68generates an alarm. Also, if the processor 53 detects any abnormalitiesin the system's operation an alarm signal is sent to the end uservisually, audibly, both or otherwise.

After a self-test power-up routine, there is an auto-configure processthat calibrates and setup the system. In one embodiment, a calibrationroutine can be performed to test the operation of the wrist electrodebefore starting an operation. The auto configure process can includetesting impedances and indicating if there are any problems. If thesystem passes, it will acquire baseline data from the reference orrecording electrodes. A single baseline is acquired for each stimulationset. A quality number can be assigned based on the SNR. The SNR ismeasured between the baseline noise level taken between 35 and about 50mSec for the upper SSEP and about 10 to about 25 mSec for the lower SSEPand the signal for the primary N20 to baseline and the P22 to baseline.This SNR is determined for different averaging counts. The systemauto-sets itself for an SNR greater than at least about 10 dB. Activenoise filtering can also be used to reduce unwanted noise. Afterperforming this initial set-up, a plurality of average sets, such asbetween about 3 and about 10 sets, is performed for reliability andreproducibility. These are stored and used later for comparisons ofchanges in evoked potentials over time.

A warning threshold is adjustable by the user, but a default setting isprovided in one embodiment. The alarm criteria for SSEP's can be set asa reduction in signal amplitude of about 50% and a latency shift ofabout 10% relative to a baseline set. In order to generate a warningduring an operation, the threshold can be set at an intermediate valuerelative to the alarm criteria to get a warning that something may behappening prior to this event. If the system 50 is part of theanesthesia machine, it can use data from that machine's standard monitorto help rule out anesthesia and vital effects. The processor can usethis data feed and execute software designed to identify other effectsbased on the anesthesia machine data. If the default signal amplitude isabout 40% then if that level is reached the monitoring system will checkfor possible changes in other channels and changes in the a anesthesiaand vitals and generate a warning or another indication of a potentialproblem.

The processor may be any suitable processing device or set of processingdevices, such as a microprocessor, a microcontroller-based platform, acomputer-processor such as an Intel or AMD processor, a suitableintegrated circuit, or one or more application-specific integratedcircuits (ASICs).

As generally noted above, a processor of the monitoring system isconfigured to communicate with, configured to access, and configured toexchange signals with a memory device or data storage device or anadapter. In one embodiment, the adapter is configured to cause nervesignals and associated alarms to be displayed on an anesthesia machineor collect data there from. In various embodiments, the memory device ofthe monitoring system includes random access memory (RAM), a hard drive,and other forms. In other embodiments, a memory device includes readonly memory (ROM). In certain embodiments, a memory device of themonitoring system includes flash memory and/or EEPROM (electricallyerasable programmable read only memory). It should be appreciated thatany other suitable magnetic, optical, and/or semiconductor memory mayoperate in conjunction with the monitoring system disclosed herein.

In certain embodiments, as generally described above, a memory device ofthe monitoring system stores program code and instructions executable bya processor of the monitoring system to control the monitoring system,generate threshold, and process data feeds. A memory device of themonitoring system also stores other operating data, such signal traces,electrode properties, relative electrode placement, alarm triggeringroutines, impedance information and/or applicable nerve stimulation andbaseline tracking rules. In various embodiments, part or all of theprogram code and/or the operating data described above is stored in oneor more detachable or removable memory device including, but not limitedto, a cartridge, a disk, a CD ROM, a DVD, a USB memory device, or anyother suitable non-transitory computer readable medium.

The exemplary monitoring system illustrated in FIG. 7 includes one ormore output devices. One or more output devices of the monitoring systemare one or more display devices configured to display any alert, signaltrace, or stimulation signal detected or generated by the monitoringsystem and any suitable information associated with a given monitoringperiod such as perioperative period. In certain embodiments, the displaydevices are connected to or mounted on a housing of the monitoringsystem. In various embodiments, the display device serves as multiplesource of time varying patient information.

In various embodiments, the display devices include, without limitation:a monitor, a television display, a liquid crystal display (LCD), adisplay based on light emitting diodes (LEDs), or any other suitableelectronic device or display mechanism. In certain embodiments, asdescribed above, the display device includes a touch-screen with anassociated touch-screen controller. It should be appreciated that thedisplay devices may be of any suitable sizes, shapes, and configurationsamenable for displaying patient data.

The display devices of the monitoring system are configured to displayone or more alarms, signal tracings, or other patient derived data. Incertain embodiments, one output device of the monitoring system is asound generating device. The monitoring system illustrated in FIG. 7 caninclude one or more speakers to generate an indication of an alarm orthat a patient needs to be moved to ameliorate the neuropathy.

In one embodiment, the system of FIG. 7 can either be part of ananesthesia machine or a stand-alone monitoring system. Each SSEP can bedisplayed for user evaluation, yet the main interface is a color codedor symbol coded output. These outputs can be configured to indicate anormal system and signal, an abnormal signal, or a system error thatincludes.

There are one or more indicators configured to display systeminformation. Three can be used as shown in FIG. 8 in one embodiment. Oneor more indicators can be configured to indicate that (1) All electrodeimpedances good or bad (stimulation, recording, and ground) and anindication of which is bad (red) or good (green); (2) System status(Booting up (yellow flashing), operational (green), impedance testing(blue), initial baseline (flashing green), system error (red)); and (3)all normal light (green when no issues—red when there is an issue). Fora stand-alone monitoring unit, each electrical or evoked potentialwaveform is displayed with its baseline. For the anesthesiabased-system, any waveform can be displayed by choosing a configurationwindow. The percentage change from a baseline of each evoked potentialwave peak or amplitude value can be shown using various indicators.Various other indicators and graphical interfaces can be used. In oneembodiment, the point in which the amplitude decreases by about 50%and/or the latency increases by 10% is when an alarm is triggered. Abridge to the temperature sensor to define the proper latency change canbe used since temperature is a normal reason for latency to change. Thiscan improve the accuracy of alarm triggers.

An example of changed signal is shown in FIG. 9 and more particularly inFIGS. 10B and 10C. These figures show a user interface screenshotdisplayed in an embodiment suitable for use in the operating room. Thetop panels are from stimulation at the left wrist and the bottom panelsare from stimulation at the right wrist in FIG. 9. The left to rightsequence of panels show the responses from stimulation of the followingnerves: Ulnar, Median, and Radial in FIG. 9. The arrows indicatesignificant changes when stimulating both the medial and radial nerve onthe left wrist. They also show no change occurring when stimulating theulnar nerve and no change when stimulating the right side. Thisexemplary data set was obtained using the electrode array configurationof FIGS. 2 and 3.

Non-Limiting Software Features and Embodiments for Implementing SSEPMonitoring Methods and Systems

The following description is intended to provide an overview of devicehardware and other operating components suitable for performing themethods of the invention described herein. This description is notintended to limit the applicable environments or the scope of theinvention. Similarly, the hardware and other operating components may besuitable as part of the apparatuses described above. The invention canbe practiced with other system configurations, including personalcomputers, multiprocessor systems, microprocessor-based or programmableelectronic device, network PCs, minicomputers, mainframe computers, andthe like.

Some portions of the detailed description are presented in terms ofalgorithms and symbolic representations of operations on data bitswithin a computer memory. These algorithmic descriptions andrepresentations can be used by those skilled in the computer andsoftware related fields. In one embodiment, an algorithm is here, andgenerally, conceived to be a self-consistent sequence of operationsleading to a desired result. The operations performed as methods stopsor otherwise described herein are those requiring physical manipulationsof physical quantities. Usually, though not necessarily, thesequantities take the form of electrical or magnetic signals capable ofbeing stored, transferred, combined, transformed, compared, andotherwise manipulated.

Unless specifically stated otherwise as apparent from the followingdiscussion, it is appreciated that throughout the description,discussions utilizing terms such as averaging, thresholding,determining, generating, alarming or the like, refer to the action andprocesses of a computer system, processor, circuit or similar electronicdevice, that manipulates and transforms data represented as physical(electronic) quantities within electronic registers and memories intoother data similarly represented as physical quantities within thecomputer system memories or registers or other such information storage,transmission or display devices.

The present invention, in some embodiments, also relates to apparatusfor performing the operations herein. This apparatus may be speciallyconstructed for the required purposes, or it may comprise a generalpurpose computer selectively activated or reconfigured by a computerprogram stored in the computer.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct more specializedapparatus to perform the required method steps. The required structurefor a variety of these systems will appear from the description below.

Embodiments of the invention may be embodied in many different forms,including, but in no way limited to, computer program logic for use witha processor (e.g., a microprocessor, microcontroller, digital signalprocessor, or general purpose computer), programmable logic for use witha programmable logic device, (e.g., a Field Programmable Gate Array(FPGA) or other PLD), discrete components, integrated circuitry (e.g.,an Application Specific Integrated Circuit (ASIC)), or any other meansincluding any combination thereof. In a typical embodiment of thepresent invention, some or all of the processing of the data collectedusing the electrodes and received by the system is implemented as a setof computer program instructions that is converted into a computerexecutable form, stored as such in a computer readable medium, andexecuted by a microprocessor under the control of an operating system.Thus, evoke potential signals captured by reference electrodes aretransformed into processor understandable instructions suitable forgenerating alarms and nerve signal data and other features andembodiments described above.

Computer program logic implementing all or part of the functionalitypreviously described herein may be embodied in various forms, including,but in no way limited to, a source code form, a computer executableform, and various intermediate forms (e.g., forms generated by anassembler, compiler, linker, or locator). Source code may include aseries of computer program instructions implemented in any of variousprogramming languages (e.g., an object code, an assembly language, or ahigh-level language such as Fortran, C, C++, JAVA, or HTML) for use withvarious operating systems or operating environments. The source code maydefine and use various data structures and communication messages. Thesource code may be in a computer executable form (e.g., via aninterpreter), or the source code may be converted (e.g., via atranslator, assembler, or compiler) into a computer executable form.

The computer program may be fixed in any form (e.g., source code form,computer executable form, or an intermediate form) either permanently ortransitorily in a tangible storage medium, such as a semiconductormemory device (e.g., a RAM, ROM, PROM, EEPROM, or Flash-ProgrammableRAM), a magnetic memory device (e.g., a diskette or fixed disk), anoptical memory device (e.g., a CD-ROM), a PC card (e.g., PCMCIA card),or other memory device. The computer program may be fixed in any form ina signal that is transmittable to a computer using any of variouscommunication technologies, including, but in no way limited to, analogtechnologies, digital technologies, optical technologies, wirelesstechnologies (e.g., Bluetooth), networking technologies, andinternetworking technologies. The computer program may be distributed inany form as a removable storage medium with accompanying printed orelectronic documentation (e.g., shrink-wrapped software), preloaded witha computer system (e.g., on system ROM or fixed disk), or distributedfrom a server or electronic bulletin board over the communication system(e.g., the Internet or World Wide Web).

Hardware logic (including programmable logic for use with a programmablelogic device) implementing all or part of the functionality previouslydescribed herein may be designed using traditional manual methods, ormay be designed, captured, simulated, or documented electronically usingvarious tools, such as Computer Aided Design (CAD), a hardwaredescription language (e.g., VHDL or AHDL), or a PLD programming language(e.g., PALASM, ABEL, or CUPL).

Programmable logic may be fixed either permanently or transitorily in atangible storage medium, such as a semiconductor memory device (e.g., aRAM, ROM, PROM, EEPROM, or Flash-Programmable RAM), a magnetic memorydevice (e.g., a diskette or fixed disk), an optical memory device (e.g.,a CD-ROM), or other memory device. The programmable logic may be fixedin a signal that is transmittable to a computer using any of variouscommunication technologies, including, but in no way limited to, analogtechnologies, digital technologies, optical technologies, wirelesstechnologies (e.g., Bluetooth), networking technologies, andinternetworking technologies. The programmable logic may be distributedas a removable storage medium with accompanying printed or electronicdocumentation (e.g., shrink-wrapped software), preloaded with a computersystem (e.g., on system ROM or fixed disk), or distributed from a serveror electronic bulletin board over the communication system (e.g., theInternet or World Wide Web).

Various examples of suitable processing modules are discussed below inmore detail. As used herein a module refers to software, hardware, orfirmware suitable for performing a specific data processing or datatransmission task. Typically, in a preferred embodiment a module refersto a software routine, program, or other memory resident applicationsuitable for receiving, transforming, routing and processinginstructions, or various types of data such as baseline nerve signals,average sets, amplitude percentage changes, latency values, stimulationsignals, post-stimulation nerve signals, electrode array configurationinformation, neuropathy types, alert thresholds, predetermined deviationlimits, and other data.

Computers and computer systems described herein may include operativelyassociated computer-readable media such as memory for storing softwareapplications used in obtaining, processing, storing and/or communicatingdata. It can be appreciated that such memory can be internal, external,remote or local with respect to its operatively associated computer orcomputer system.

Memory may also include any means for storing software or otherinstructions including, for example and without limitation, a hard disk,an optical disk, floppy disk, DVD (digital versatile disc), CD (compactdisc), memory stick, flash memory, ROM (read only memory), RAM (randomaccess memory), DRAM (dynamic random access memory), PROM (programmableROM), EEPROM (extended erasable PROM), and/or other likecomputer-readable media.

In general, computer-readable memory media applied in association withembodiments of the invention described herein may include any memorymedium capable of storing instructions executed by a programmableapparatus. Where applicable, method steps described herein may beembodied or executed as instructions stored on a computer-readablememory medium or memory media. These instructions may be softwareembodied in various programming languages such as C++, C, Java, and/or avariety of other kinds of software programming languages that may beapplied to create instructions in accordance with embodiments of theinvention.

The aspects, embodiments, features, and examples of the invention are tobe considered illustrative in all respects and are not intended to limitthe invention, the scope of which is defined only by the claims. Otherembodiments, modifications, and usages are apparent to those skilled inthe art without departing from the spirit and scope of the claimedinvention.

The use of headings and sections in the application is not meant tolimit the invention; each section can apply to any aspect, embodiment,or feature of the invention.

Throughout the application, where compositions are described as having,including, or comprising specific components, or where processes aredescribed as having, including or comprising specific process steps, itis contemplated that compositions of the present teachings also consistessentially of, or consist of, the recited components, and that theprocesses of the present teachings also consist essentially of, orconsist of, the recited process steps.

In the application, where an element or component is said to be includedin and/or selected from a list of recited elements or components, itshould be understood that the element or component can be any one of therecited elements or components and can be selected from a groupconsisting of two or more of the recited elements or components.Further, it should be understood that elements and/or features of acomposition, an apparatus, or a method described herein can be combinedin a variety of ways without departing from the spirit and scope of thepresent teachings, whether explicit or implicit herein.

The use of the terms “include,” “includes,” “including,” “have,” “has,”or “having” should be generally understood as open-ended andnon-limiting unless specifically stated otherwise.

The use of the singular herein includes the plural (and vice versa)unless specifically stated otherwise. Moreover, the singular forms “a,”“an,” and “the” include plural forms unless the context clearly dictatesotherwise. In addition, where the use of the term “about” is before aquantitative value, the present teachings also include the specificquantitative value itself, unless specifically stated otherwise.

It should be understood that the order of steps or order for performingcertain actions is immaterial so long as the present teachings remainoperable. Moreover, two or more steps or actions may be conductedsimultaneously.

Where a range or list of values is provided, each intervening valuebetween the upper and lower limits of that range or list of values isindividually contemplated and is encompassed within the invention as ifeach value were specifically enumerated herein. In addition, smallerranges between and including the upper and lower limits of a given rangeare contemplated and encompassed within the invention. The listing ofexemplary values or ranges is not a disclaimer of other values or rangesbetween and including the upper and lower limits of a given range.

It should be appreciated that various aspects of the claimed inventionare directed to subsets and substeps of the techniques disclosed herein.Further, the terms and expressions employed herein are used as terms ofdescription and not of limitation, and there is no intention, in the useof such terms and expressions, of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed. Accordingly, what is desired to be secured by LettersPatent is the invention as defined and differentiated in the followingclaims, including all equivalents.

What is claimed is:
 1. A nerve monitoring system comprising a wristbandcomprising a first pair of electrodes, a second pair of electrodes, athird pair of electrodes, and an elongate flexible substrate, firstelectrode, second electrode, and third electrode disposed in or on theflexible substrate; and a first electrical lead having an electrodecontacting end and a monitoring device contacting end, the electrodecontacting end in electrical communication with at least one electrodein the first pair of electrodes.
 2. The system of claim 1, wherein thefirst pair of electrodes is positioned relative to the elongate flexiblesubstrate such that each electrode in the first pair is positionableabove a median nerve when the wristband is worn.
 3. The system of claim2, wherein the second pair of electrodes is positioned relative to theelongate flexible substrate such that each electrode in the second pairis positionable above a radial nerve when the wristband is worn.
 4. Thesystem of claim 3, wherein the third pair of electrodes is positionedrelative to the elongate flexible substrate such that each electrode inthe third pair is positionable above an ulnar nerve when the wristbandis worn.
 5. The system of claim 1, wherein the flexible substrate hasone or more demarcations configured to identify a boundary between oneor more nerves or bones disposed relative to nerves.
 6. The system ofclaim 1 further comprising a second electrical lead having an electrodecontacting end and a monitoring device contacting end, the electrodecontacting end in electrical communication with at least one electrodein the second pair of electrodes.
 7. The system of claim 6 furthercomprising a third electrical lead having an electrode contacting endand a monitoring device contacting end, the electrode contacting end inelectrical communication with at least one electrode in the third pairof electrodes.
 8. The system of claim 1 further comprising a monitoringdevice in electrical communication with the monitoring device contactingend of the first electrical lead, the monitoring device configured tostimulate one or more electrodes in the first electrode pair and monitorresponsive signals from one or more of a radial, ulnar or median nerve.9. The system of claim 8 wherein the monitoring device comprises ahousing, one or more electrode input ports configured to connect to oneor more electrical leads, a processor disposed in the housing, a memorystorage device configured to store measured baseline signals, a timerconfigured to synchronize pulse delivery, a pulse generator configuredto transmit a plurality of pulses along the first electrical lead, acomparator configured to detect deviations in responsive nerve signalsgenerated following pulse delivery to a nerve, and an alarm generatorconfigured to indicate a change from a first patient state to a secondpatient state, the memory storage device, the timer, the pulsegenerator, and the comparator in electrical communication with andresponsive to processor control signals.
 10. The system of claim 8further comprising an adapter configured to interface with an anesthesiamachine such that alerts, nerve signals, or combinations thereof arepresented on a display of the anesthesia machine.
 11. A processor-basedmethod of detecting a neuropathy in a patient comprising noninvasivelymonitoring a first nerve, a second nerve, and a third nerve, wherein thefirst nerve, the second nerve, and the third nerve are at leastpartially disposed in the wrist of the patient; electrically stimulatingthe first, second, and third nerves; detecting a deviation relative to abaseline signal with respect to a responsive signal generated by one ormore of the first, second, and third nerves following the electricstimulation using a processor; comparing the deviation to apredetermined threshold using a processor; and generating an alertindicative of the neuropathy when the deviation exceeds a predeterminedthreshold.
 12. The method of claim 11 wherein the neuropathy is aperioperative neuropathy and the alert is displayed on an anesthesiamachine.
 13. The method of claim 11 wherein the first nerve is a radialnerve, wherein the second nerve is a median nerve and wherein the thirdnerve is an ulnar nerve.
 14. The method of claim 11 further comprisingnoninvasively monitoring a fourth nerve at least partially disposedbelow a knee of the patient.
 15. The method of claim 14 wherein thefourth nerve is a posterior tibial nerve and wherein the responsivesignal is generated by one or more of the first, second, third andfourth nerves.
 16. A nerve monitoring system comprising an input portconfigured to receive a plurality of time varying electrical signalsfrom one or more reference electrodes in a non-invasive electrode array;a comparator in electrical communication with the input port; aprocessor in electrical communication with the comparator; a displaydevice in electrical communication with the processor; and a memorydevice storing a plurality of instructions which, when executed by theprocessor, cause the processor to operate with the display device andthe comparator to: (a) control the comparator and cause it to compareone or more of the plurality of time varying electrical signals to oneor more baseline signals; (b) determine when a deviation between abaseline signal and one or received signals from the electrode arrayexceeds an alarm threshold; and control the display device such that analarm signal is displayed when the alarm threshold has been exceeded.17. The nerve monitoring system of claim 16 wherein the non-invasiveelectrode array is configured to collect signals from N+M positions on apatient by contacting a skin surface without piercing the same.
 18. Thenerve monitoring system of claim 17 wherein the electrode arraycomprises N anode and cathode pairs and M reference electrodes such thateach anode and cathode in a pair is positioned to stimulate one or moremonitored nerves and each reference electrode is positioned to measureone or more baseline nerves or baseline positions.
 19. The nervemonitoring system of claim 18 wherein N is greater than or equal to sixand M is six.
 20. The nerve monitoring system of claim 18 wherein themonitored nerves comprise a radial nerve of a first hand, an ulnar nerveof the first hand, a median nerve of the first hand, a radial nerve of asecond hand, an ulnar nerve of the second hand, and a median nerve ofthe second hand. 21-24. (canceled)